1. Field of the Invention
The present invention relates generally to radio communication effected using impulse radio. The present invention provides a planar loop antenna that is well-suited for use with impulse radio communications. In particular, the present invention provides an antenna that is useful with wireless local area network (LAN) systems including laptop computer or other portable communication devices. The antenna of the present invention is especially useful with PCMCIA (Personal Computer Memory Card International Association) card implementations of wireless modem devices for use with portable communication devices, such as lap top computers. There is a need for compact antennas having a radiation pattern similar to a loop antenna. In particular there is a need for such an antenna that is useful for broadband communications. It would be especially useful for such a loop-type antenna to handle impulse radio communications in an ultra wideband environment.
2. Related art
Recent advances in communications technology have enabled an emerging, revolutionary ultra wideband technology (UWB) called impulse radio communications systems (hereinafter called impulse radio).
Impulse radio was first fully described in a series of patents, including U.S. Pat. Nos. 4,641,317 (issued Feb. 3, 1987), 4,813,057 (issued Mar. 14, 1989), 4,979,186 (issued Dec. 18, 1990) and 5,363,108 (issued Nov. 8, 1994) to Larry W. Fullerton. A second generation of impulse radio patents include U.S. Pat. Nos. 5,677,927 (issued Oct. 14, 1997) to Fullerton et al; and 5,687,169 (issued Nov. 11, 1997) and 5,832,035 (issued Nov. 3, 1998) to Fullerton. These patent documents are incorporated herein by reference.
Uses of impulse radio systems are described in U.S. patent application Ser. No. 09/332,502, entitled, xe2x80x9cSystem and Method for Intrusion Detection Using a Time Domain Radar Array,xe2x80x9d and U.S. patent. application Ser. No. 09/332,503, entitled, xe2x80x9cWide Area Time Domain Radar Array,xe2x80x9d both filed the same day as the present application, Jun. 14, 1999, both of which are assigned to the assignee of the present invention, and both of which are incorporated herein by reference.
Basic impulse radio transmitters emit short pulses approaching a Gaussian monocycle with tightly controlled pulse-to-pulse intervals. Impulse radio systems typically use pulse position modulation, which is a form of time modulation where the value of each instantaneous sample of a modulating signal is caused to modulate the position of a pulse in time.
For impulse radio communications, the pulse-to-pulse interval is varied on a pulse-by-pulse basis by two components: an information component and a pseudo-random code component. Unlike direct sequence spread spectrum systems, the pseudo-random code for impulse radio communications is not necessary for energy spreading because the monocycle pulses themselves have an inherently wide bandwidth. Instead, the pseudo-random code of an impulse radio system is used for channelization, energy smoothing in the frequency domain and for interference suppression.
Generally speaking, an impulse radio receiver is a direct conversion receiver with a cross correlator front end. The front end coherently converts an electromagnetic pulse train of monocycle pulses to a baseband signal in a single stage. The data rate of the impulse radio transmission is typically a fraction of the periodic timing signal used as a time base. Because each data bit modulates the time position of many pulses of the periodic timing signal, this yields a modulated, coded timing signal that comprises a train of identically shaped pulses for each single data bit. The impulse radio receiver integrates multiple pulses to recover the transmitted information.
In a multi-user environment, impulse radio depends, in part, on processing gain to achieve rejection of unwanted signals. Because of the extremely high processing gain achievable with impulse radio, much higher dynamic ranges are possible than are commonly achieved with other spread spectrum methods, some of which must use power control in order to have a viable system. Further, if power is kept to a minimum in an impulse radio system, this will allow closer operation in co-site or nearly co-site situations where two impulse radios must operate concurrently, or where an impulse radio and a narrow band radio must operate close by one another and share the same band.
An apparatus for conveying electromagnetic energy intermediate a host device and a medium substantially adjacent to the apparatus includes: (a) a transceiving structure for transmitting the energy to the medium and receiving the energy from the medium; (b) a transmission structure for conveying signals representing the energy to the host device or from the host device; and (c) a feed structure coupling the transceiving structure with the transmission structure. The transceiving structure includes a substantially planar metal layer arrayed upon a dielectric substrate. The metal layer is bounded by a first edge and a second edge. The first edge and the second edge cooperate to form a bight having a first arm and a second arm establishing a metal-free area intermediate the first arm and the second arm. The first arm presents a first terminal locus and the second arm presents a second terminal locus. The feed structure is coupled with the first and second terminal loci to effect the coupling.
It is an object of the present invention to provide an antenna that is useful with wireless local area network (LAN) systems including laptop computer or other portable communication devices.
It is a further object of the present invention to provide an antenna that is useful with PCMCIA card implementations of wireless modem devices for use with portable communication devices, such as lap top computers.
A further object of the present invention is to provide an antenna that is compact and has a radiation pattern similar to a loop antenna.
Still a further object of the present invention is to provide an antenna that is useful for broadband or multi-band operation.
Another object of the present invention is to provide an antenna that is a loop-type antenna capable of handling impulse radio communications in an ultra wideband environment.
Further objects and features of the present invention will be apparent from the following specification and claims when considered in connection with the accompanying drawings, in which like elements are labeled using like reference numerals in the various figures, illustrating the preferred embodiments of the invention.